This diagram shows the following zones:

• the external Internet, outside the DMZ firewall

• the Web Server Tier DMZ, between the DMZ firewall and the Intranet firewall

• the Infrastructure DMZ, inside the Web Server Tier DMZ, but separated from the other parts of DMZ by the Infrastructure firewall

  the corporate intranet, behind the Intranet firewall.

The external Internet contains the external clients, which communicate across the DMZ Firewall with the Load Balancer.

The Web Server Tier DMZ contains the Load Balancer, which communicates with the OracleAS Single Sign-On and OC4J for Single Sign-on servers, as well as with Oracle Web Cache, and Oracle HTTP Server, and Business Intelligence and Forms. The Web Server Tier DMZ also contains the Infrastructure DMZ.

There is a note under the combined Web Cache, and Oracle HTTP Server, and Business Intelligence and Forms servers saying "If you are running Portal, the oc4j_portal instance running the parallel page engine and the HTTP Server for the oc4j_portal instance must run on the same computer."

Within the Web Server Tier DMZ:

• The Load Balancer communicates through the DMZ Firewall with external clients using HTTP or HTTPS.

• The Load Balancer communicates with the Oracle HTTP Server for Single Sign-on and OC4J for Single Sign-On. The Load Balancer also communicates with the Web Cache, and Oracle HTTP Server, and Business Intelligence and Forms servers.

• Oracle HTTP Server communicates through the Infrastructure Firewall with Oracle Internet Directory using SQL*Net.

• Web Cache, and Oracle HTTP Server, and Business Intelligence and Forms communicate through the Infrastructure Firewall to Oracle Internet Directory using SQL*Net. They also communicate through the Intranet Firewall to the Customer Database using SQL*Net.

The Infrastructure DMZ contains Real Application Clusters, the OracleAS Metadata Repository, including product metadata, management metadata, and security metadata, and Oracle Internet Directory. Oracle Internet Directory communicates across the Infrastructure Firewall using SQL*Net. It communicates with the Oracle HTTP Server, and Web Cache, and Business Intelligence and Forms in the Web Server Tier DMZ, using SQL*Net.

The corporate intranet contains the customer database with business data, possibly in Real Application Clusters or a cold failover cluster. The customer database communicates using AJP with the J2EE servers in the Webserver Tier DMZ. It also communicates using SQL*Net with Web Cache in the Webserver Tier DMZ.